A Second Outer-Core Region in Klebsiella pneumoniae Lipopolysaccharide

Abstract

ABSTRACT Up to now only one major type of core oligosaccharide has been found in the lipopolysaccharide of all Klebsiella pneumoniae strains analyzed. Applying a different screening approach, we identified a novel Klebsiella pneumoniae core (type 2). Both Klebsiella core types share the same inner core and the outer-core-proximal disaccharide, GlcN-(1,4)-GalA, but they differ in the GlcN substituents. In core type 2, the Glc p N residue is substituted at the O-4 position by the disaccharide β-Glc p (1-6)-α-Glcp(1, while in core type 1 the Glc p N residue is substituted at the O-6 position by either the disaccharide α-He p (1-4)-α-Kdo(2 or a Kdo residue (Kdo is 3-deoxy- d -manno-octulosonic acid). This difference correlates with the presence of a three-gene region in the corresponding core biosynthetic clusters. Engineering of both core types by interchanging this specific region allowed studying the effect on virulence. The replacement of Klebsiella core type 1 in a highly type 2 virulent strain (52145) induces lower virulence than core type 2 in a murine infection model.